Transistor-negative resistance diode circuits using d.c. feedback



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TRANSISTOR-NEGATIVE RESISTANCE DIODE CIRCUITS USING D.C. FEEDBACK Filed April 19, 1961 IN VEN TOR. ffaa i H5006' 3,408,592 Patented Oct. 29, 1968 United States Patent-Drre 3,408,592 e f TRANSISTOR-NEGATIVE RESISTANCE. DIODE CIRCUITS USING D.C. FEEDBACKl Gerald B. Herzog, Princeton, NJ., assignor to Radio Corporation of America, a corporation of Delaware Filed Apr. 19, 1961, Ser. No. 104,165 f 9 Claims. (Cl. S31- 8)` This ivention relates to electrical circuits, and more particularly to wave generating circuitsl for producingrecur'- rent signal waveforms.

An electrical circuit, such as a wave generatingi circuit, in accordance with the invention includes 'a transistor and trode of transistor. f

A suitable control signal, such as derived from a phase detector responsive to the output signal of the wave generating circuit, "-may .be utilized to additionally bias the negative resistance diode and provide an automatic control of the -requency of the output signals from'the circuit. f

The invention may be more fully understood when thel following detailed description is read in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic circuit diagram of a wave generating clrcuit in accordance with the invention;

2 is a graph showing curves illustrating certain operational features of the circuit of FIGURE 1; and

FIGURE 3 is a graph showing curves illustrating output signals that may be derived from the circuit of FIG- URE l.

The Wave generating circuit shown in FIGURE 1 includes a transistor transistor is illustrated as a PNP transistor and the -B, is thus negative diode 18 has its cathode connected and the base 20, and the base through a resistor 24 to a control 26. A charging capacitor 28 is connected directly l:between appear at a pair of output terminals 30 and 30', with the output 30 connected to the collector 14 and the terminal 30' connected directly to ground.

Output signals at the collector 14 are also applied directly from the collector 14 to a phase detector 32, the function of which will be explained hereinafter.

To simplify the description, the operation of the circuit will be described, initially, assuming that the phase detector 32 is not connected in the circuit.

When the operating lvoltage, -B, is applied to the circuit, the lvoltage across the tunnel diode 18 is initially zero placing a zero bias between the emitter 12 and -base 20 of the transistor 10 and biasing the transistor 10 to a cut-01T condition where no current ows between co1- 2v lector 14 and emitter 12. This condition V.bestillustrated in lwhich the curve 34-34 curve 36-.36'V is a plot of the current-voltage characteristicshof the .baseto-emitter path of the transistor 10. Because the tunnel diode 187 land the Ibasefto-emitter path are connected in paralleL, the composite characteristic of thetwo is obtained, by adding thel two curves 34-34.. and 36-36. The resultant composite-characteristic isA -shown as the partially dashed curve 343738.,The initial zero voltage across the tunnel diode 18 is shownA as point 40- on the composite curve 34-,-37-38, indicating the low voltag ,state of the tunnel diode; y

`Because atthe initial `condition described the. transistor 10 With the tunnel diode The output waveform Ifrom the circuit of FIGURE 1 is shown in FIGURE 3A, which is a p lot of the output voltage appearing at the terminals 30-30' against time. The downward sloping portions 48 of the curves shown in FIGURE 3A represent the charging of the capacitor in its low voltage state, that is, during the time required 'for the operating point of the tunel diode 18 to move from point 40 to point 42 on the composite curve 34-37-38 shown in FIG- URE 2. The upward sloping portions 50 of the curves 36-47-40 shown in FIGURE The circuit of the invention lends itself readily to automatic frequency control of the output signal. If, for indirection,

UREv 2.

quired to reach ,the peak current point v42 of the Ytunnel diode 18 is increased, since a larger voltage between the -collector 14 and ground is now needed to drive the tunnel diode 18to its ,peak current point.42..Since-,the. capaci- 28 must lnow charge for a longer. time, at.I decrease in the fequency of lth e,output` signal resultss shown in Thev downward sloping portions 48 Aof FlGURl-l again/'represent the harg' y g of capacitor 28 apdtlie upw'arduslopin'g porn'ons4 r450'11"I "resent'the capacifor discharge, xNc'ntetha't the p eak`valu'e-of'thevoltage appearin'gwatthe collector 1 4 must become more n e'gativeyto rey'e'rse biasatfthe" control terminal ,2 6jto causo" the"tunnel' diodeh|18 to switch solas to disclarg the `capacitra28 throughl the 4ransistor 71,0., on the otherhanma'negtive direct control voltage isl appliedt'o" the control terminal 2,6, 'the opposite action occurs. In this case the tunnel diode'18 is vbiased in the forward directionvand its initial operating point is shifted from poin" i I combinedlcharacteri'stic 34%37438. A smaller' than normal voltage Y orith'e collector 14 will drive the tunnel diode 18 to lits peak curretpoin't 42 and initiate the action previously described to discharge the capacitor 28. This is illustrated in FIGURE 3C, in which the downward sloping portions 38" represent the charging of capacitor 28 and upward sloping portions 50 represent the capacitor discharge. Note that the frequency of the recurrent wave,- form is increased while its amplitude is decreased.

The frequency of the circuit is automatically controlled by the phase detector 32 which receives as an input signal the output waveform available across the capacvtor 28. The phase detector 32 may be of well known design to provide a positive output signal when the frequency of the output wave is greater than desired and a negative output signal when the frequency of the output signal is lower than desired.

As is also well known, the frequency and/or phase of the output signal rnay also be compared in the phase detector 32 with an external synchronizing signal (shown as applied to phase detector 32 via' lead 33) as, for instance, in presently available commercial television receivers.

A practical circiut constructed in accordance with the invention may have typical values as follows:

Operating voltage, -B volts -28 Resistor 16 ohms-- 10,000 Resistor 22 do 10,000 Resistor 24 ..do 10,000 Capacitor 28 microfarad 0.015 Transistor Type 2N109 Tunnel diode 18 (1) 1G'ermanium tunnel diode millamperes.

With the circuit values shown and with the circuit free running (that is with the voltage at the control terminal Z6 equal to zero) the frequency of the output saw-tooth signal is 15.4 kilocycles. Values of the frequency of the output signal for various control voltages are as follows:

lmvlng a peak current of 2.5

Control voltage:

Frequency, kilocycles +1.35 11.3 +1.25 12.0 +1.0 13.3 +05 14.5 +0 15.4 +0.25 15.9 0.5 16.4 0.75 16.7 1.0 17.0 1.5 17.6 2.0 17.8 -2.5 18.2

While a type PNP transistor has been illustrated in the circuit of FIGURE 1, it is to be understood that the circuit may be operated in the same manner using an Thus, lthe charging time of the capacitor 48rre-Q" NPN transistor requiring only a reversal in polarity of the operating voltage and a reversal in the connection of the tunnel diode 18, that is,: ,its anode is connected to the base 20 of the transistor 10-'and its cathode to the emitter 1. r' .Y A *t 2.a' if, r w'f'qu 1.y The combination comprising aQtran'sistor having input, .outputfan'dpommon electrodes, arnegative, resistance diodepf the ,voltagecontrolled type havingyhigh` and low voltage statesjoonneeted between said inputielctrode and said common electrode# in'a *polarity to maintain said transistor cpt-off when said diode'is in saidlow voltage sta'te va'ri'dtofcanse conduction 'in saidf transistor' when said diode is 'insaid high `voltage"'state,' means includingan impedancev for coupling a source of'unidirectional v oltage between said output andfs'ai'd commonelect'rodes, and adirect currentv feedback connection rn'eaiis' between said output 'electrode and said input electrode toswitch said diode between said bigband Ilowvoltage"states. "2. The combination comprising'a transistor having base, emitter, and collector electrodes, a tunnel diode connected between said base' 'and emitter electrodes in a polarity"t maintain' said transistor cut-olfI when said diode is in'a low voltage state and'to cause conduction in said transisto'r when said diode is in a high voltage state, means in cluding an' impedance for applying an energizing unidirectional potential to said collector electrode, and direct current feedback means connected from said collector electrode to saidy diode to switch said diode between said high and low voltage states in responseto the voltage lon said collector electrode. 4

3. The combination comprising a transistor having base, emiter, and collector electrodes; biasing means for said transistor including a negative resistance diode'of the voltage controlled type having high and low voltage states connected between said base and emitter electrodes and poled to maintain said transistor cut-olf when said diode is in said-low voltage state and to cause 'conduction in said transistorvwhen said diode is in said high voltage state; means including a'resistor for applying and operating voltage to said collector electrode; direct current feedback means connected between said collector electrode and said diode to switch said diode between said high and Ilow voltage states in response to the voltage of said collector electrode, said feedback means including a feedbackresistor for controlling the amount of direct current back; and a reactive element associatedl with said collector electrode for controlling the time of application of said direct current feedback.

44'. Awave generating circuit comprising in combination a transistor having base,` emitter and collector elec# trodes, a negative resistance diode of the voltage controlled type connected between said emitter and base electrodes and poled to cut-off said transistor when said diode'is in a lowA voltage state and to cause conduction in said transistor when said diode is in a high voltage state, means including a first resistor for applying an operating voltage to said collector electrode, a capacitor connected between saidcollector and emitter electrodes,feedback means iricluding a-second resistor connected between said collector and base electrodes for switching said diode between its high and low voltage states in response to the voltage on said'collector electrode, and means for deriving an output signal from said collector electrode.

5. A wave generating circuit comprising in combination a transistor having base, emitter and collector electrodes, a negative resistance diode of the connected between said emitter and base electrodes and poled to cut-off said transistor when said diode-is in a low voltage state and to cause conduction in said transistor when said diode is in a high voltage state, means including a rst resistor for applying an operating voltage 'to said collector electrode, a capacitor connectedl between said collector and emitter electrodes, feedback means including a second resistor connected between said collectorL and base electrodes for switching said diode between its voltage controlled type high and low voltage sta-tes in response to the voltage on aid ollector electrode, means trode.

6. A sawtooth wave combination a transistor having base,

poled to cut-01T` collector-to-emitter current in s-aid transistor when said diode is in said low voltage state and to cause collector-to-emitter current confrom said collector electrode, phase detector means having an input circuit and an output circuit for developing a control voltage in said output circuit in response to a sig al applied References Cited UNITED STATES PATENTS 2,766,380 10/ 1956 Kroger 331-8 3,094,630 6/1963 Rapp et al. 307-88.5 3,094,631 6/1963 Davis 307-88.5 3,102,209 8/1963 Pressman 307-88.5 3,116,459 12/1963 Tiemann 307-885 OTHER REFERENCES Tunnel Diode Manual General Electric Co., 44-49.

Tunnel Diodes as Amplifiers and Switches, by Sylvan et al. in reprint of May 1960 issue of Electric Equipment Engineering, 7 pages.

JOHN KOMINSKI, Primary Examiner. J. A. JORDAN, Assistant Examiner.

TK, 7872, S4G4, copyrighted Mar.

1st edition, by 20, 1961, pp. 

1. THE COMBINATION COMPRISING A TRANSISTOR HAVING INPUT, OUTPUT AND COMMON ELECTRODES, A NEGATIVE RESISTANCE DIODE OF THE VOLTAGE CONTROLLED TYPE HAVING HIGH AND LOW VOLTAGE STATES CONNECTED BETWEEN SAID INPUT ELECTRODE AND SAID COMMON ELECTRODE IN A POLARITY TO MAINTAIN SAID TRANSISTOR CUT-OFF WHEN SAID DIODE IS IN SAID LOW VOLTAGE STATE AND TO CAUSDE CONDUCTION IN SAID TRANSISTOR WHEN SAID DIODE IS IN SAID HIGH VOLTAGE STATE, MEANS INCLUDING AN IMPEDANCE FOR COUPLING A SOURCE OF UNIDIRECTIONAL VOLTAGE BETWEEN SAID OUTPUT AND SAID COMMON ELECTRODES, AND A DIRECT CURRENT FEEDBACK CONNECTION MEANS BETWEEN SAID OUTPUT ELECTRODE AND SAID INPUT ELECTRODE TO SWITCH SAID DIODE BETWEEN SAID HIGH AND LOW VOLTAGE STATES. 